The most widely studied coronal abundance anomaly is the so-called "FIP effect", where the abundances of elements with low First Ionization Potential (FIP) are enhanced relative to the photosphere. Many studies in the past have reported a tendency for more active stars to have less of a FIP effect, and for particularly active stars to even exhibit an inverse FIP effect, where low FIP elements are depleted in the corona instead of enhanced. However, we find that this activity dependence is nonexistent among main sequence stars when the most active stars with log LX > 29 are excluded. Extremely active stars normally dominate coronal surveys since active stars are brighter and more easily observed in X-rays, but by avoiding such extremes and focusing solely on more normal stars we find a very different empirical view of the FIP effect, one in which FIP bias is dependent on spectral type instead of activity. This dependence indicates a strong connection between coronal abundance and basic photospheric characteristics.
16th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun
- Pub Date:
- December 2011